Bi-Stable Valve

ABSTRACT

A bi-stable valve includes a first chamber having a first aperture and a second aperture, and a second chamber having a first aperture and a second aperture. The bi-stable valve also includes a shaft having a first valve member adjacent a first end of the shaft and a second valve member adjacent an opposite second end of the shaft. The shaft is movable between a first position, in which the first valve member closes off the second aperture of the first chamber and the second valve member closes off the second aperture of the second chamber to prevent fluid from passing through the second apertures of the first and second chambers, and a second position, in which the first valve member and the second valve member allow fluid to pass through the second aperture of the first chamber and the second aperture of the second chamber.

This application is a continuation application of U.S. patentapplication Ser. No. 12/955507, filed Nov. 29, 2010.

BACKGROUND

In the drilling of oil and gas wells, a drill bit is typically locatedat the end of a drill string. Rotation of the drill string causes thedrill bit to drill into the well. It may be necessary in certainsituations to deviate from drilling the well in a vertical direction.This is referred to as directional drilling. A known method ofdirectional drilling includes the use of a rotary steerable system. Insuch systems, down hole devices steer the drill bit in a desireddirection.

The rotary steerable system can include a bias unit that is locatedadjacent to the drill bit. The bias unit applies force to the drill bitin a controlled direction while the drill string rotates. The bias unitincludes a plurality of bias pads that are actuated by drilling fluid ormud through a valve. The valve actuates the bias pads by sequentiallydiverting the drilling fluid into the piston chamber of each pad. Eachbias pad is movable between a retracted position and an extendedposition in which the bias pad is positioned against the wall of thewell. The drill bit can be urged in a desired direction by controllingthe movement of the bias pads.

The manufacture and maintenance of conventional valves may be complex.Conventional valves generally limit the rotational speed of the drillbit to a maximum rotational speed of 200 RPM due in part to limitedbackflow capability of conventional valves.

SUMMARY

In one exemplary embodiment, a bi-stable valve includes a first chamberhaving a first aperture and a second aperture, and a second chamberhaving a first aperture and a second aperture. The bi-stable valve alsoincludes a shaft having a first valve member adjacent a first end of theshaft and a second valve member adjacent an opposite second end of theshaft. The shaft is movable between a first position (a closedposition), in which the first valve member closes off the secondaperture of the first chamber and the second valve member closes off thesecond aperture of the second chamber to prevent fluid from passingthrough the second apertures of the first and second chambers, and asecond position (an open position), in which the first valve member andthe second valve member allow fluid to pass through the second apertureof the first chamber and the second aperture of the second chamber. Abi-stable actuator can be provided to control the movement of the shaft.

In another exemplary embodiment, a downhole tool control system includesa plurality of bi-stable valves, each of which includes the featuresdescribed above. The control system includes a common inlet conduit influid communication with the first aperture of the first chamber and thefirst aperture of the second chamber of each of the bi-stable valves.

A downhole bi-stable valve is provided in another exemplary embodiment.The downhole bi-stable valve includes a first state in which an exhaustport and a pad port are exposed to a first pressure and an inlet port isexposed to a second pressure greater than the first pressure, and asecond state in which the exhaust port, the pad port, and the inlet portare exposed to the second pressure. The valve is pressure balanced inboth the first state and the second state.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects, features, and advantages ofexemplary embodiments will become more apparent and may be betterunderstood by referring to the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of a drilling installation that shows anexemplary bottom hole assembly;

FIG. 2 is a schematic view of an exemplary single stage pressurebalanced bi-stable valve;

FIG. 3 is a schematic view similar to the view shown in FIG. 2, wherethe bi-stable valve is in a closed position;

FIG. 4 is a schematic view similar to the view shown in FIG. 2, wherethe bi-stable valve is in an open position;

FIG. 5 is a schematic view similar to the view shown in FIG. 2, where apad is being discharged when the bi-stable valve is in a closedposition; and

FIG. 6 is a schematic view of an exemplary down hole tool control systemthat includes a plurality of bi-stable valves;

FIG. 7 is a schematic view similar to the view shown in FIG. 6, whereone of the pads is being charged and another pad is being discharged;

FIG. 8 is a schematic view similar to the view shown in FIG. 6, whereone of the pads is being charged and another pad is being discharged;

FIG. 9 is a schematic view similar to the view shown in FIG. 6, whereone of the pads is being charged and another pad is being discharged;and

FIG. 10 is a schematic view similar to the view shown in FIG. 6, whereone of the pads is being charged and another pad is being discharged.

DETAILED DESCRIPTION

The exemplary embodiments taught herein are described in connection witha pressure balanced single stage bi-stable valve that is used in adownhole tool control system. It should be understood, however, that theteachings herein can be used with other types of valves.

In order to fully understand the advantages of the bi-stable valve, abrief overview of a bottom hole assembly 10 is provided in FIG. 1. Thebottom hole assembly 10 may include a drill bit 12 which is connected toa lower end of a drill string 14. A bias unit 16 is connected to thedrill bit 12 and a control unit 18 is provided to control the operationof the bias unit 16. The bias unit 16 may be controlled to apply alateral bias to the drill bit 12 in a desired direction to control thedirection of drilling.

The bias unit 16 includes a plurality of pads 20 movable betweenextended and retracted positions. Each of the pads 20 is supplied withdrilling fluid or mud under pressure through a bi-stable valve (notshown in FIG. 1). The bi-stable valve actuates the pads 20 bysequentially diverting the drilling fluid into chambers formed in eachpad 20.

FIGS. 2-4 illustrate an exemplary embodiment of a pressure balancedsingle stage bi-stable valve 22 of the present invention. The valve,designated generally as 22, is adapted to regulate the flow of adrilling fluid or mud to a pad, such as one of the pads 20 (see FIG. 1).Drilling fluid is delivered to the valve 22 through an inlet 24 and isdischarged from the valve 22 through an exhaust 26.

Referring to FIGS. 2-4, the valve 22 is equipped with a first chamber28, a pad inlet chamber 30 (a second chamber 30), a pressure balancingchamber 32 (a third chamber 32), and a fourth chamber 34 in oneexemplary embodiment. The first chamber 28 is located adjacent to thethird chamber 32, while the second chamber 30 is located adjacent to thefourth chamber 34. While four chambers are shown, it will be understoodthat the labeling and sizing of the chambers can vary.

The first chamber 28 includes a first aperture 36 and a second aperture38, and the second chamber 30 includes a first aperture 40 and a secondaperture 42. The third chamber 32 includes a first aperture 44 and asecond aperture 46, and the fourth chamber 34 includes a first aperture48, a second aperture 50, and a third aperture 52. The second aperture38 of the first chamber 28 is in fluid communication with the firstaperture 44 of the third chamber 32. Also, the second aperture 42 of thesecond chamber 30 is in fluid communication with the first aperture 48of the fourth chamber 34. It will be understood that the number ofapertures in each chamber can vary. In some embodiments, there can onlybe a single aperture between the first chamber 28 and the third chamber32, and there can only be a single aperture between the second chamber30 and the fourth chamber 34.

The diameters of the apertures formed in the chambers 28, 30, 32, 34 canbe different from each other. For example, in one exemplary embodiment,the diameter of the second aperture 38 of the first chamber 28 isgreater than the diameter of the second aperture 42 of the secondchamber 30.

An inlet conduit 54 extends between the inlet 24, the first chamber 28,and the third chamber 32. The inlet conduit 54 is in fluid communicationwith the first aperture 36 of the first chamber 28 and the firstaperture 40 of the second chamber 30.

An exhaust conduit 56 extends between the exhaust 26, the third chamber32, and the fourth chamber 34. The exhaust conduit 56 is in fluidcommunication between the second aperture 46 of the third chamber 32 andthe second aperture 50 of the fourth chamber 34.

A pad conduit 58 extends from the fourth chamber 34 to the pad 20. Thepad conduit 58 is in fluid communication with the third aperture 42 ofthe fourth chamber 34.

The valve 22 includes a shaft 60 having a first valve member 62 adjacenta first end 64 of the shaft 60, and a second valve member 66 adjacent anopposite second end 68 of the shaft 60. The first valve member 62 of theshaft 60 is located adjacent to the first chamber 28, and the secondvalve member 66 of the shaft 60 is located adjacent to the secondchamber 30.

A bi-stable actuator 70 (shown schematically as “BSA” in the figures) isprovided to move the shaft 60 between a first closed position (a firststate) as shown in FIG. 2 and a second open position (a second state) asshown in FIG. 3. In the closed position (see FIG. 2), the first valvemember 62 is adjacent to the second aperture 38 of the first chamber 28and closes off the second aperture 38 of the first chamber 28 to preventfluid from passing to the third chamber 32. The second valve member 66is positioned adjacent to the second aperture 42 of the second chamber30 and closes off the second aperture 42 of the second chamber 30 toprevent fluid from passing to the fourth chamber 34. In this manner, thefirst chamber 28 is fluidly isolated from the third chamber 32, and thesecond chamber 30 is fluidly isolated from the fourth chamber 34.

When the actuator 70 moves the shaft 60 to the open position (see FIG.3), the shaft 60 extends into the third chamber 32. This causes thefirst valve member 62 to move away from the second aperture 38 of thefirst chamber 28 to thereby allow fluid to pass through the secondaperture 38 of the first chamber 28 to the third chamber 32. This alsocauses the second valve member 66 to move away from the second aperture42 of the second chamber 30 to thereby allow fluid to pass through thesecond aperture 42 of the second chamber 30 to the fourth chamber 34. Inthis manner, the first chamber 28, the second chamber 30, the thirdchamber 32, the fourth chamber 34, the pad conduit 58, and the exhaustconduit 56 are fluidly coupled to each other so as to allow the flow offluid therethrough, thereby charging the pad 20.

In one exemplary embodiment, a restrictor 72 is provided to restrict theshaft 60 from extending into the fourth chamber 34. In another exemplaryembodiment, the shaft 60 can be prevented from extending into the fourthchamber 34 or moving further into the third chamber 32 by internalrestrictors of the actuator 70, which is dictated by the efficiency ofthe circuitry of the actuator 70.

In operation, the valve 22 may initially be in the closed position (seeFIGS. 2 and 3), although it can be in the open position as well.Drilling fluid F is delivered under pressure through the inlet 24. Thedrilling fluid then flows through the inlet conduit 54. A portion of thedrilling fluid F flows to the first chamber 28, while the other portionof the drilling fluid F flows to the third chamber 32. Because the firstvalve member 62 closes off the second aperture 38 of the first chamber28, fluid F is prevented from passing through the second aperture 38 ofthe first chamber 28 and remains in the first chamber 28. Likewise,because the second valve member 66 closes off the second aperture 42 ofthe second chamber 30, fluid F is prevented from passing through thesecond aperture 42 of the second chamber 30 and remains in the secondchamber 30. This prevents fluid F from flowing to the pad conduit 58 andto the exhaust conduit 56.

The first and second chambers 28, 30 and the inlet conduit 54 areexposed to a high hydrostatic pressure when the valve 22 is in theclosed state. This is because flow of fluid is restricted to the firstand second chambers 28, 30 and the inlet conduit 54. The hydrostaticpressure acting in a first direction against the first valve member 62is substantially balanced by hydrostatic pressure acting in an oppositedirection against the second valve member 66. Because of the lack ofpressure differential, the valve 22 is pressure-balanced when the shaft60 is in the closed position. In one exemplary embodiment, the maximumhydrostatic pressure can be 850 PSI, and the differential pressure canbe in a range from 450 PSI to 850 PSI. Those skilled in the art wouldappreciate that because the valve 22 is pressure-balanced, as such themaximum pressure differential is limited by the structural strength ofthe valve parts under tension, which, in turn depends on the selectionof materials and the sizes of the valve components.

It should be noted that the force required by the actuator 70 to movethe shaft 60 is proportional to the differential pressure. Because thevalve 22 is pressure-balanced, the actuator 70 requires less force tomove the shaft 60 compared to prior art valves where the valve is notpressure-balanced.

Turning now to FIG. 4, the shaft 60 is moved to the open position by theactuator 70. In particular, the first valve member 62 moves away fromthe second aperture 38 of the first chamber 28 to thereby allow fluid Fto pass through the second aperture 38 of the first chamber 28 to thethird chamber 32. The second valve member 66 moves away from the secondaperture 42 of the second chamber 30 to thereby allow fluid F to passthrough the second aperture 42 of the second chamber 30 to the fourthchamber 34. After passing through the third chamber 32 and the fourthchamber 34, fluid F flows through the exhaust conduit 56 to the exhaustand through the pad conduit 58 to the pad 20.

The pad conduit 58, the exhaust conduit 56, the inlet conduit 54, andthe chambers 28, 30, 32, 34 are exposed to high hydrostatic pressurewhen the valve 22 is in the open position. This is because fluid F flowsthrough the pad conduit 58, the exhaust conduit 56, the inlet conduit54, and the chambers 28, 30, 32, 34. Because of the lack of pressuredifferential, the valve 22 is pressure-balanced when the shaft 60 is inthe open position.

In one exemplary embodiment, the relative flow of fluid through thechambers 28, 30, 32, 34, the pad conduit 58, the exhaust conduit 56, andthe inlet conduit 54 can be controlled. For example, an orifice of thepad conduit 58 can have a larger size than an orifice of the exhaustconduit 56 such that fluid flow through the pad conduit 58 is lessrestricted than fluid flow through the exhaust conduit 56.

Referring to FIG. 5, the shaft 60 is moved from the open position to theclosed position by the actuator 70 to discharge fluid F from the pad 20.Because the first valve member 62 closes off the second aperture 38 ofthe first chamber 28, fluid F from the inlet conduit 54 is preventedfrom passing through the second aperture 38 of the first chamber 28 andremains in the first chamber 28. Likewise, because the second valvemember 66 closes off the second aperture 42 of the second chamber 30,fluid F from the inlet conduit 54 is prevented from passing through thesecond aperture 42 of the second chamber 30 and remains in the secondchamber 30. This prevents additional fluid from flowing to the padconduit 58 and to the exhaust conduit 56. The existing fluid in the pad20 is discharged or exhausted through the pad conduit 58, the fourthchamber 34, and the exhaust conduit 56 to the exhaust 26.

The first and second chambers 28, 30 and the inlet conduit 54 areexposed to a high hydrostatic pressure when the valve 22 is in theclosed state and the pad 20 is discharged. This is because high pressureflow of fluid is restricted to the first and second chambers 28, 30 andthe inlet conduit 54. The pad conduit 58 and the exhaust conduit 56 areexposed to a low hydrostatic pressure because fluid F in the pad 20 isdischarged through the pad conduit 58 and the exhaust conduit 56 andadditional high pressure fluid is prevented from entering the padconduit 58 and the exhaust conduit 56. Because of the lack of pressuredifferential, the valve 22 is pressure-balanced when the shaft 60 is inthe closed position and the pad 20 is being discharged.

When the pad 20 is discharged, certain components of the valve 22, suchas the third and fourth chambers 32, 34, the pad conduit 58, and theexhaust conduit 56, are not exposed to high pressure fluid flow. Thus,these components of the valve 22 are resistant to erosion.

The exemplary embodiments of the valve 22 allows a downhole tool toachieve a higher RPM than conventional prior art valves. That is, theexemplary embodiments of the valve 22 permits dumping due to backflowfrom a discharging pad line at high RPMs. In various exemplaryembodiments, the RPM can be in a range of 600 RPM to 700 RPM. Bycontrast, conventional rotary valves are limited to a maximum RPM ofbetween 180 and 220 RPMs. Those skilled in the art would appreciate thatin other embodiments other RPMs greater than the conventional maximumlimit are achievable depending on such factors, such as the distancebetween the valve 22 and the pad 20, internal restrictions in chargingand discharging conduits, moment of inertia of the bias unit, etc.

FIG. 6 is a downhole tool control system 74 that includes a plurality ofbi-stable valves 22A-D in an exemplary embodiment. In particular, thecontrol system 74 includes a first valve 22A, a second valve 22B, athird valve 22C, and a fourth valve 22D. Each of the valves 22A-Dcooperates with a respective pad 20 and a respective exhaust 26. Whilefour valves are shown, it will be understood that the number andarrangement of the valves can vary.

The control system 74 includes a common inlet conduit 76 that is influid communication with the first aperture 36 of the first chamber 28and the first aperture 40 of the second chamber 30 of each of the valves22A-D. Each of the valves 22A-D is adapted to individually regulate theflow of fluid F to a separate pad 20. In particular, each pad conduit 58of each valve 22A-D is in fluid communication with a respective one ofthe plurality of valves 22A-D to separately control a plurality of pads20.

Fluid F is delivered to each valve 22A-D through the common inletconduit 76 and is discharged from each valve 22A-D through a separateexhaust 26. In particular, each exhaust conduit 56 of each valve 22A-Dis in fluid communication with a respective one of the plurality ofvalves 22 to provide separate exhausts 26 for each of the plurality ofvalves 22A-D.

The shaft 60 of each of the plurality of valves 22A-D is individuallycontrollable to move between the closed position and the open positionto selectively charge and discharge the plurality of pads 20. Forexample, FIG. 7 shows the control system 74 with one of the pads(identified as PAD 1) being charged and another pad (identified as PAD4) being discharged. FIG. 8 shows the control system 74 with one of thepads (identified as PAD 2) being charged and another pad (identified asPAD 1) being discharged. FIG. 9 shows the control system 74 with one ofthe pads (identified as PAD 3) being charged and another pad (identifiedas PAD 2) being discharged. FIG. 10 shows the control system 74 with oneof the pads (identified as PAD 4) being charged and another pad(identified as PAD 3) being discharged.

While the pressure-balanced single-staged bi-stable valve 22 has beenshown in use with a four-pad rotary drilling tool, the bi-stable valve22 can be used with any number of pads. Each pad can be separatelycontrolled by a single valve.

The control system 74 provides for better controllability of thefour-pad rotary drilling tool compared to a conventional control systemthat includes two bi-stable valves that control four pads. Also, thecontrol system 74 is more reliable than conventional control systemssince the failure of one of the bi-stable valves 22 does not result inthe failure of the three remaining bi-stable valves 22. As a result, therotary drilling tool does not completely lose the ability to steer.Additionally, the control system 74 results in lower backflow and higherresultant force of the bias unit compared to conventional controlsystems in view of the individual exhaust lines 56 of the valves 22A-D.

It will be understood that the embodiments described herein are merelyexemplary and that a person skilled in the art may make many variationsand modifications without departing from the spirit and scope of theinvention. All such variations and modifications are intended to beincluded within the scope of the invention as defined by the appendedclaims.

What is claimed is:
 1. A down hole tool control system, comprising: aplurality of bi-stable valves, each of the valves comprising: a firstchamber having a first aperture and a second aperture; a second chamberhaving a first aperture and a second aperture; a shaft having a firstvalve member adjacent a first end of the shaft and a second valve memberadjacent an opposite second end of the shaft, the shaft movable betweena first position, in which the first valve member closes off the secondaperture of the first chamber and the second valve member closes off thesecond aperture of the second chamber to prevent fluid from passingthrough the second apertures of the first and second chambers, and asecond position, in which the first valve member and the second valvemember allow fluid to pass through the second aperture of the firstchamber and the second aperture of the second chamber; a third chamberhaving a first aperture and a second aperture, the first aperture influid communication with the second aperture of the first chamber; and afourth chamber having a first aperture, a second aperture and a thirdaperture, the first aperture of the fourth chamber in fluidcommunication with the second aperture of the second chamber; a commoninlet conduit in fluid communication with the first aperture of thefirst chamber and the first aperture of the second chamber of theplurality of bi-stable valves.
 2. The down hole control system of claim1, wherein the each valve comprises a pad conduit in fluid communicationwith a pad such that each bi-stable valve can operate the respective padbetween an extended position and a retracted position.
 3. The down holecontrol system of claim 2, wherein the pad conduit is in fluidcommunication with the third aperture of the fourth chamber.
 4. The downhole control system of claim 2, wherein the each valve comprises anexhaust conduit in fluid communication with the second aperture of thethird chamber and the second aperture of the fourth chamber.
 5. The downhole control system of claim 1, wherein: the pad conduit is in fluidcommunication with the third aperture of the fourth chamber; and in thefirst position the pad conduit and the exhaust conduit are fluidlycoupled.
 6. The down hole control system of claim 1, wherein: the padconduit is in fluid communication with the third aperture of the fourthchamber; and in the second position, the first chamber, the secondchamber, the third chamber and the fourth chamber are fluidly coupled.7. A bottom hole assembly, comprising: a bias unit connected to a drillbit, the bias unit having a plurality of pads each moveable betweenextended and retracted positions; and a control unit comprising aplurality of bi-stable valves to control the operation of the bias unit,each valve comprising: a first chamber having a first aperture and asecond aperture; a second chamber having a first aperture and a secondaperture; a shaft having a first valve member adjacent a first end ofthe shaft and a second valve member adjacent an opposite second end ofthe shaft, the shaft movable between a first position, in which thefirst valve member closes off the second aperture of the first chamberand the second valve member closes off the second aperture of the secondchamber to prevent fluid from passing through the second apertures ofthe first and second chambers, and a second position, in which the firstvalve member and the second valve member allow fluid to pass through thesecond aperture of the first chamber and the second aperture of thesecond chamber; a third chamber having a first aperture and a secondaperture, the first aperture in fluid communication with the secondaperture of the first chamber; a fourth chamber having a first aperture,a second aperture and a third aperture, the first aperture of the fourthchamber in fluid communication with the second aperture of the secondchamber; and a pad conduit in fluid communication with one pad of theplurality of pads.
 8. The bottom hole assembly of claim 7, wherein eachpad of the plurality of pads can be operated between the extendedposition and the retracted position separate from the control of theother pads of the plurality of pads.
 9. The bottom hole assembly ofclaim 7, wherein the each valve comprises an exhaust conduit in fluidcommunication with the second aperture of the third chamber and thesecond aperture of the fourth chamber.
 10. The bottom hole assembly ofclaim 7, comprising a common inlet conduit in fluid communication withthe first aperture of the first chamber and the first aperture of thesecond chamber of the plurality of bi-stable valves.
 11. The bottom holeassembly of claim 10, wherein the each valve comprises an exhaustconduit in fluid communication with the second aperture of the thirdchamber and the second aperture of the fourth chamber.
 12. The bottomhole assembly of claim 7, wherein: the pad conduit is in fluidcommunication with the third aperture of the fourth chamber; and in thefirst position the pad conduit and the exhaust conduit are fluidlycoupled.
 13. The bottom hole assembly of claim 7, wherein: the padconduit is in fluid communication with the third aperture of the fourthchamber; and in the second position, the first chamber, the secondchamber, the third chamber and the fourth chamber are fluidly coupled.